The Queen officially declared the Games open the previous night during director Danny Boyle's raucous, pop culture-themed opening ceremony.
Widely hailed as showcasing an inventive, and sometimes eccentric, ceremony, the show included a short film featuring Daniel Craig, the latest actor to play cinematic British spy James Bond, and the queen herself.
As the first rounds of the tennis tournament began, Swiss star Roger Federer returned to the All-England Club where he won the Wimbledon men's singles title only three weeks ago.
Meanwhile, Britain's hopes in Saturday's 250-kilometer cycling road race, in which newly crowned Tour de France champion Bradley Wiggins sought to aid fellow Briton Mark Cavendish to a medal, were dashed as Kazakhstan's Alexander Vinokourov put in a gutsy sprint to take the gold.
Thousands of spectators had lined the route through the streets of London and along leafy roads in neighboring Surrey to catch a glimpse of the riders racing by. Organizers also predict big crowds on Sunday for the women's cycling road race, as tickets aren't needed to watch the action.
Olympic fans, many dressed up in their national colors, packed outdoor viewing areas in Hyde Park and elsewhere to watch the day's events unfold on a big screen.
The government said in a statement Saturday that plans for the management of crowds, security and transport appeared to be going well so far, including the exit of large crowds from the Olympic Stadium following the late-night opening ceremony.
Concerns had been raised ahead of the Games about the capacity of London's already busy transport network to deal with the hordes of visitors heading to the Olympic Park and other venues.
Security also became an issue ahead of the Games when the private contractor G4S revealed it could not provide as many security guards as required. The British military has stepped in to fill the gap.
Beijing bronze medal winner Russia defeated Canada on Saturday as women's basketball started, while later in the day, Team USA routed Croatia by a score of 81-56.
All teams may be trying to keep the U.S. women from winning their fourth straight gold medal. Team USA has played Australia for gold in each of the past three Olympics. Australia, led by 6-foot-5 Lauren Jackson, starts play late Saturday against Team GB.
Team USA's Dana Vollmer also set a new Games best of 56.25 seconds in the qualifying heats of the women's 100-meter butterfly.
Earlier Saturday, Russia's Arsen Galstyan prevailed over Hiroaki Hiroaka of Japan, pinning the contest favorite to take his first gold medal in the men's 60-kilogram judo competition.
And Australia tallied its first gold medal of the games Saturday with a win in the women's swimming 4x100m freestyle relay. The Netherlands took the silver and the United States won bronze.